N-Ray vs. X-Ray (What's the Difference?)

Neutron radiography (N-ray or NR) and X-radiography (X-ray)
are complementary non-destructive testing techniques. In
both cases, a form of radiation passes through the object
being imaged, and then exposes a photographic film. The type
of radiation used in neutron radiography is neutrons, while
the type of radiation used in X-radiography is X-rays. Neutron
radiographs and X-radiographs show different characteristics
of the object imaged due to differences in neutron and X-ray
interaction with the material that the object is made up
of (see
Figure 1).

The images shown below provide good examples of the differences
between neutron radiography and X-radiography.

Liquids, such as the lighter fluid shown in the lighter image,
plastics, rubbers, ceramics and lubricants show up very well
in neutron radiographs, while metal components show up well
in X-ray images. Due to the relative invisibility of metals
to neutrons, neutron radiography can be used to effectively
image items encased in metal. The variation in images produced
using neutron radiography and X-radiography makes the two
complementary technologies, both very useful
for particular applications.

Figure (a)
Liquids, such as the lighter fluid shown in the image above,
as well as, plastic components, rubbers, ceramics and lubricants
show up very brightly in neutron radiographs, while metals
show up well in X-ray images. For this reason, neutron radiography
is well suited to imaging various materials encased in metals.

Figure (b)
Internal chambers, passage ways and details in metal parts,
such as the quick-disconnect fitting shown above, can be imaged
very clearly using neutron radiography. x-radiography is more
suited to imaging metal inclusions in other materials.

Figure (c)
The internal structure, air pathways and blockages or inclusions
in metal alloy turbine blades can be imaged very clearly using
neutron radiography. Even areas surrounded by several centimeter
thickness material, such as the turbine blade root holes shown
in the image above, can be imaged very effectively. X-radiography
is more suited to imaging metals inside of other materials.

Figure 1

Figure 1
– While the probability of x-ray interaction with matter
increases with the target material atomic number, the probability
of neutron interaction with matter is random with respect
to the target material atomic number. Neutron attenuation
by matter depends on the material properties, specifically
the neutron cross-section.